The variation of bulk density with composition across a miscibility gap is adequately described by a simple model in which volume additivity of the two phases is assumed. The density-weight percent composition function must always have positive (concave-upward) curvature across a two-phase region. The density-mole percent composition function can have either positive or negative curvature, depending upon the location of the miscibility gap in the binary diagram and upon the molecular weights of the end-member oxides. Immiscible composition regions are generally signalled more clearly by simple density-weight percent composition plots than by density-mole percent plots or molar volume or partial molar volume analyses. The model is used to predict possible immiscible regions in the system K2OSiO2, PbOSiO2, B2O3GeO2, SiO2GeO2, PbOGeO2, and PbOP2O5. Immiscibility is probably not present on the GeO2-rich side of the alkali germanate series of glasses. The LiF-rich limit of the miscibility gap in the LiF-BeF2 system is estimated.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry